This invention relates to planar optical waveguides and a method of making the waveguides.
Optical fiber communication systems are becoming prevalent. The optical fiber system can comprise an optical fiber, and a wide variety of other optical devices for receiving, transmitting, and using signals. Optical waveguides, which provide a means of receiving and processing signals from optical fibers, have proven to be useful devices in optical fiber systems.
The present invention features a novel optical waveguide comprising an optical confinement layer. The waveguide has a lower cladding layer, a core layer, a patterned optical confinement layer proximate to the core layer, an optional upper cladding layer, and an optional substrate. The optical confinement layer may comprise, e.g., MgF2, LiF, or any other low index material. The core layer may comprise a high index silica doped with, e.g., aluminum, titanium, tantalum, zirconium, germanium, hafnium,or phosphorus. Alternatively, the core layer may comprise silicon oxynitride (SiON) or silicon nitride (Si3N4). The cladding layers may comprise silica. For example, the lower cladding layer may comprise a low index silica that may be doped with boron or fluorine. The substrate may comprise silicon or silica. Alternatively, the cladding layers and core layer may each comprise a polymer. In some embodiments, the waveguide may include layers doped with rare earth elements, such as erbium.
The location of the optical confinement layer may vary as long as it is proximate to the core layer. For example, the optical confinement layer can be between the lower cladding layer and core layer, between the upper cladding layer and core layer, embedded in the core layer, embedded in the upper cladding layer, or embedded in the lower cladding layer.
As used in this invention:
xe2x80x9coptical confinement layerxe2x80x9d means a layer in an optical waveguide device, distinct from the core layer and the cladding layer, having a refractive index lower than that of the cladding layer, and patterned so as to laterally guide light in the waveguide; and
xe2x80x9clateralxe2x80x9d directions refer to directions in the plane of the optical confinement layer.
An advantage of at least one embodiment of the present invention is ease of manufacture. In some embodiments, this invention allows fabrication of waveguides using simple photolithography and lift-off patterning techniques, eliminating the need for reactive ion etching (and the associated equipment costs), and minimizing the number of processing steps required.
Another advantage of at least one embodiment of the present invention is low optical loss. In some embodiments, this invention uses very thin layers for lateral optical confinement layers. Because of the thinness of these layers, they may be patterned smoothly and precisely using lift-off or etching techniques, thereby minimizing optical losses due to scattering.
Another advantage of at least one embodiment of the present invention is that the resultant device can have a substantially planar surface, which can be useful for applications in which that surface is to be bonded to a submount. Such applications include those in which the waveguide is to be aligned with another device.
Other features and advantages of the invention will be apparent from the following drawings, detailed description, and claims.